In general, continuous ink jet printing apparatus have a printhead manifold to which ink is supplied under pressure so as to issue in streams from a printhead orifice plate that is in liquid communication with the cavity. Periodic perturbations are imposed on the liquid streams, such as vibrations by an electromechanical transducer, to cause the streams to break-up into uniformly sized and shaped droplets.
Orifice plates with arrays containing thousands of nozzles are required for page-wide continuous ink jet printheads. All of the nozzles must be perfectly formed, all being of uniform size and free of deformities such as flat edges. The nozzles, which are typically about 25 micron diameter, require submicron smoothness. This requires that great care must be exercised to provide metallic substrates free of micron-sized defects.
Highly polished metallic substrates can be made by diamond polishing. However, this is an expensive process that imparts high cost to the substrate that can be used only once. Additionally, even diamond polishing cannot ensure that every blemish is removed. Hence, small pits can result in defective holes and rejection of entire orifice arrays.
Still other prior art for making orifice plates include permanent mandrels for plating of orifice plates. This method includes plating of thin single layer orifice plates onto metalized glass substrates. This provides the desired smooth surfaces. As the orifice plate can be peeled off from the metalized glass subtrates, this method eliminates the need for corrosive etching away of the substrate, with the inherent environmental and safety hazards associated therewith. It has been found, however, that the high stresses developed during plating of the thick, multi-layer orifice plates causes the electroformed orifice plates to delaminate from the metallized substrates, making this method unsuitable for plating of thick, multi-layer orifice plates.
It is seen then that there is a need for an improved substrate that is more readily separable from electroformed orifice plate structures, to overcome the problems associated with the prior art.